1. Field of the Invention
The invention relates to a bell of transparent vitreous silica for purposes relating to semiconductor technology, particularly to an epitaxy bell, having a flange consisting of fused silica material and welded to the constricted end from which a process gas is exhausted during operation, and having a flange of opaque fused silica welded to the opposite end at which the process gas enters.
2. Discussion of Prior Art
Bells of the kind described above are known and are used for growing monocrystalline silicon on silicon semiconductor chips. The bells are usually operated in the vertical position. In the known bells, the welded flange consists of a cylindrical opaque fused silica body having marginal fins made by sawing. An annular transparent fused silica plate is welded onto this opaque fused silica body. For the support of this flange of such very complex construction, the transparent fused silica plate is welded at its outside margin to a hollow cylinder of transparent fused silica, whose other end is welded to the tapered bell portion.
The known bells of transparent fused silica have proven effective in operation, but on account of the complex construction of the flange they are made at the cost of a large amount of labor, so that they are rather expensive and also easily broken.